1. Field of the Invention
The present invention relates to a method and apparatus for forming a composite image.
2. Description of the Prior Art
It is possible to form an image from a number of smaller images. Typically, these smaller images are stitched together to form the larger image. In order to do this, each smaller image must have an area of overlap with adjacent smaller images so that the larger image is continuous. In order to align the smaller images, it is known to select a large number of so-called “correspondence points” in each image. A correspondence point is a point in two adjacent smaller images which represent the same point in the scene. This assists in making the larger image appear continuous.
However, this method has two problems. Firstly, in order to ensure that the smaller images are as closely aligned as possible, a large number of correspondence points are required. Specifically, it is typical that these points are spread over a large area. This means that a large area of overlap is required between adjacent smaller images and so the resolution of the larger image is reduced. Secondly, because the cameras capturing the smaller images can never be exactly co-located, straight lines that traverse the boundaries of the smaller images when stitched to form the larger image are distorted. Typically, this is exhibited as a kink in the line.
It is an aim of the present invention to alleviate these problems.